Due to shortcomings in previous genetic approaches (the inability to distinguish developmental defects from the pathogenesis occurring in the matured lungs and the lack of desirable cell-type specificity for genetic modifications in ECs and aSMCs), the cellular mechanisms that determine how PHD2 deficiency initiates and promotes pulmonary artery hypertension remains incompletely known. This evidence concerns the gene EGLN1 and pulmonary arterial hypertension.